Pressure-operated switch



A. 8. C088" PRESSURE OPERATED SWITCH. APPLICATIQN'FILED NOV.23, 1917.

Patented m 14 1 922;

wrmya UNITED STATES PATENT' OFFICE.

' ALBERT B. COBB, BOSTON, MASSACHUSETTS, ASSIGNOR TO COBB ELECTRIC APPLI- ANCE COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MASSACHU- SETTS.

PRESSURE-OPERATED SWITCH.

Specification of Letters Patent. Patented Feb, 14;, 1922.

Application filed November 23, 1917. Serial No. 203,615.

To all whom it may concern l Be it known'that I ALBERT 13. Conn, a citizen of the United States, residing at Bo's-' ton, in the county of Suffolk and State of Massachusetts, have invented new and useful Improvements in Pressure-Operated Switches, of which the following is a specification.

The object of the present inventionlis to provide a switch for opening and closing an electric heating circuit, said switch being controlled. by the pressure of steam or other.

' vapor generated by the heater whereof the circuit is thus controlled. A further object is to providemeans by which such a switch will remain closed as. long'as the pressure referred to is less than a certain predetermined maximum, and will be opened whenever the pressurereaches or exceeds this maximum; and to enable adjustments to be made for causing the switcht'o be opened and closed at various degrees of pressure, withoutincreasing the liability of the switch contacts to fuse together. 'A further object I 25- is to provide a safety means by which to short circuit the heating circuit, or otherwise effect a complete cutting out of the heater or heating means, in case theswitchcontacts should fail to separate at the given condition of pressure. The means by which these objects are accomplished, and the principles fundamentaltheretoare setforth in the following specification, in connectionwith one embodiment of such means,,. and are recited in the appended claims. 1

In the drawing, Figure 1 is a front elevation of a pressure gage having my improvement applied thereto, the same being represented with the dial and pointer removed in order-to'show-moreb clearly the parts wherein'the invention is particularly comprised. I Figure 2 is a sectional view'enlarged of j Figure 3' is a sectional. view enlarged of the complemental switch 'contact and the holder thereof. i F

Figure 4 is'a diagram illustrating theelectrical connections.

T he same reference characters indicate the same parts in all the figures. l

Referring to the drawing, 6 represents the' case enclosing switch and 7 represents a pressure measuring element, here shown as a curved spring tube offlattened. cross section,

constituting the common Bourdon spring generally used in pressure gages to operate the indicating ointer'. A link 8 is pivoted to the free en of the spring tube upon a finger 9 of the latterand is pivoted at'its other end' to an arm 10 onfa gear segment 11 'which actuates the indicating hand or gointer. It may be assumed without special escrlption that such segment actuates any ofthe mechanisms commonly used in pres sure gages to move an indicating hand or pointer comformabl'y to the pressure impell-. ing the spring, or that the pressure-measuring element is coupled by any other operative means to accomplish the same end.

The pivot pin 12 between the link 8 and arm 10 projects forward andunderlies an t arm 13 carried by a plunger or slide 14 which is confined and is movable endwise in a guide 15 which is supported in any suitable manner on a convenient part of the case or the frame which holds the transmission" mechanism. This guide is here shown (F igure 2) as a cylinder open at one end in which the slide 14 fits, and having an orifice in the other end through which the shank 16 of the slide passes, said orifice being surrounded b'yanabutment shoulder 17 between which and-the plunger 14: is confined a spring 18.-

'The arm 13 projects laterally through a slot 20 in the side of the guide, whereby a certain amount of endwise movement of the slide is permitted. This slide or plunger carries a switch contact 21.

The complemental contact is shown at 22 i adjacent to the contact 21 and in the line of movement thereof. Contact 22 is mount- .ed on a plug having a shank 23 which enters the bore of a tubular screw 24 which passes through the side of the case without touching it and is threaded adj ustably through a conducting block 25 which is mounted on the inside of the case upon the lateral wall thereof. The plug 23 is movable endwise, with respect to'the screw 24, but is yieldingly held therein, and preserved in electrical contact therewith, by a wire 26 one end of which is's ecured to the plug and the other end to the screw, both points of connectionbeing electrically conductive, being secured by solder or otherwise. This wire'is coiled through part of its length so as to permit its extension and also to cause it to act as a spring yieldingly holding the plug 23 in the screw.

so tal contact 21 is connected by a-wire c with one of the line wires. The third contact 27 lated therefrom. All these posts Both the conducting block 25 and the guide are insulated from the case, by

connecting wires thereto in the usual manner or other proper way. The post '28 is connected by-a wire 30 with the block 25, and

. through the latter and screw '24, wire 26,

and plug 23 with the contact 22. A wire 31 passes from the binding post 29 to the shank 16 of the slide which carries the contact 21,

and is thereby connected with the latter.

The diagram in Figure 4 shows the manher in which the contacts 21, 22,- and 27 are c'oupled'in circuit. In thisdiagram a and- -b are the line wires carrying the current One supply. 0 represents a heating coil.

' terminal-of this coil connected'by wire d withxthe contact 22, while the complemenis interposedin the run from the line wire a, to thejbther terminal of the heating coil, this run being represented by the wires f and g.

, It will now be seen that when the contacts 21 and 22 are brought together the break represented by the dotted line it is closed,

whereby current. may flow from the line through the heating coil. and back; but when the arm 13, which is joined to the contact2l touches the contact 27, the gap represented by the broken linelais closed. Thereby a short circuit between, the line wires is .established, which results in blowing out a fuse, .or otherwise action.

The operation offth'e apparatus is as fol-' lows. When the pressure is at thelowest. degree, the Bourdon spring contracts to the smallest radius and the pin 12 is moved so i 1 as to allow the contact 21,. impelled by the spring 18, and by gravity also when the gage isfset in an. upright position, to touch con tact 22. This contact is maintained as long as'the pressure is below the given point at j which the circuit is to 'be broken. vYVhen the pressure rises, pin 12 is movedand ultimately engages and lifts the 'arm 13, there by separating the contact 21' from 22.. If' these. contacts should become fused together,

or in other words and using the common term of the practical art, if the contacts should freeze, they will failto separate,

putting the line out of but by reason of theloose; mounting of the plug 23, the latter is able to follow the movement of the receding contact 21. until the arm 13 strikes the contact'27 and-establishes the short circuit which puts the entire line out of action. That is, contact 22 is mounted movably-so that accidental freezing will not prevent the free distortion of the springtube, but will permit the latter to move as designed, with results as described.

, The wire 26 establishes a good and sufficient connection of the contact 22 in the circuit,

and its spring construction holds the con- I tact back when the switch is opened in the normal manner.

The foregoing description is made with reference tothe particular form of the in-' vention here illustrated, and is not intended to limit my protection otherwise'than as appears from the express terms'of the appended claims. The fundamental principles may be embodied in various modes of mounting and adjusting the switch contacts and various modes of mounting the rela-- tively stationary contact'to travel with the relativelyv movable contact in case the two should become fused together, to accomplish the results herein described, all within the scope of the claims.

Although certain of my claims point out the safety feature of means for establishing a short circuit-in case the contacts should fuse together, other claims omit this feature because it is an emergency measure and in the normal operation of the switch does not,

come into action. The characteristics of the switch contacts and, ofv the manner in which they are mounted and adjusted enable them to carry heavy currents for long periods of-timein any position which they may occupy within their range of adjust.

ment, without being heatedto the temperature at which fusion will occur, or even to a degree high enough tofinjure them.

Pointing out these characteristics. with refere nce to the embodiment shown in the drawings, it will be noted that the contactshave contact faces of substantial width and area. which are perpendicular to the line in which the relatively movable-contact isguided and likewise to the lineor direction in which the normally stationary contact is shifted for adjustment, these two lines coinciding with one another;

remain egractly parallel to one another in any position which; the contacts may occupy gwithin their range of adjustment. When the relatively movable contact is withdrawn from the other, all points in its contacting face are removed equally at the same time from the contlguous points on the face of the other contact; and there is no reduction. in

the area of, contact when adjustment of the normally stationary contactmember is made,'

In other words the said contact or bearing surfaces uch as would occur if the contact members moved at such a time in divergent paths. Thus danger is avoided of development of high heat at the contact point, which would occur if the bearing area should be materi- .,ally diminished. Thereis also entire absence pf sliding motion between the contacts 1n opening and closing, and thus absence of any friction which might tend to cause spring. v

Another useful characteristic of the-switch is its compactness whereby it is enclosed within and protected by a cylindrical casing no larger than is necessary for the protection of the Bourdon spring. This quality'is resistance to the' movement of the Bourdon achieved by arranging. the holder or guide 15 so that the directions in which it constrains .the movable contact to travel are generally' coincident with thedirections in which thefree end of the Bourdon spring moves by pressure actuation,'and by locating this holder -largely within the continuation of the curve of the spring tube. By the last statement I do ,not mean that the holder is. necessarily in the same plane or zone with I the spring tube, but merely that it is substantially within an imaginary cylindrical surface projecting axially from the spring. The mounting ofthenormally stationary contact is arranged to suit the location of the relatively movable contact, and to permit the inclusion of its contacting end within, the, case, its adjustment in the line of movement of the'movable contact, and accessibility for being adjusted from outside the case.

The Bourdon spring may be-taken as typical offany pressure measuringor resisting element which is distorted or otherwise, moved when subjected to pressures of changing intensity, and is adapted in thus moving' to operate one or the other of the members of a switch." Since the pressure which controls theBourdon spring-is afunction of" the temperature developed in the heated fluid which actuates the spring, thisspring may be considered as indirectly 'a temperaturecontrolled element. I What I'claim and desire to secure by Letters Patent is: I I I 1. A switch comprising the combination witha member movable in consequence I of temperature changes, of complemental 'switch contacts, a tubular guide holding and making electrical connection with one of said contacts constructed-to permit movement of-such contact toward and away from the other contact, a fixed support for said other contact in which the same is adjust ably mounted with provision for adjust. ment in the same general direct-ion as the movement of the first .contact, said contacts being normally in engagement to close the electrical circuit in which they 'are a part,

andimeans by which the aforesaid member when moved by temperature increase causes the first-named contact to. be displaced from the last named contact.

, 2. An electrical switch comprising, in combination, a casing, an elongated curved member anchored at, one end in said casing and capable of moving at its other end, said member being so movable in consequence of temperature changes, a holder mounted upon said casing,"a contact piece supported by said holder and constrained thereby to move in a given path which extends in the same general direction as the path wherein the freeend of said curved member moves, a

complemental contact mounted in a normally stationary manner upon a part of said casing in a position where the first named contact may move into and out of contact with it; said contacts remaining normally in contact with one another when the temperature is belowthe point at which the switch is de-, signed to be opened, and inter-engageable projections connected with the curved member and the first-named contact arranged to engage and cause separation of said contact from the second-named contact with movement of the curved member due to temperature rise above such point.

3. An electrical switch comprising in combinationa casing, a curved spring tube flattened in cross section anchored at one end in said casing and, there having an inlet for fluid and capable of moving at itsother end, said tube being so movable in consequence of changes in the pressure of said fluid, a

holder mounted within said casing, a contact piece supported by said holder and constrained thereby to move in a given path, a complemental contact. mounted in a nor.- Inally stationary manner in a part of said casing in'a position where the first named contact may move into and out of contact with it, and connections by which the pres- 4. A pressure-operated switch comprising a casing having an encircling wall, a curved spring tube mounted in saidcasing having an inlet for admission'ofpressure fluid, one end of said tube being movable in consequence of changes in the pressure of said fluid, a guide fixed in said casing, a contact piece held by said guide andconstrained thereby to move in a given path, a complemental contactmounted upon said encircling wall and projecting toward the first-named contact piece, and operating means between the movable part of said-spring tube and the first-named'piece operative to cause the separation of the latterfrom the complemental contact piece when the spring tube is dis tor'ted 1110118 direct on.

5. A pressure-operated switch comprising a pressure-measuring movable actuating member, complemental switch contacts, one of which isrelatively stationary and the other of whichji's guided to move in a prescribed path toward and away from the first one, and means supporting the first-named contact in a manner permitting it to be moved with the second-named contact when the contacts becomefus ed together.

6. A pressure-operated switch comprising a pressure-measuring movable actuating member, complemental switch contacts, one

of which is relatively stationary" and the f other of which is guided to move in a prescribed path toward and away from the first one, means supporting, the first-named contact in af'manner permitting the latter to be moved with the second-named contactwhen the-'contactsbecome fused together, and a stationarycut-out element in position to be electrically engaged by the second-named contact in the course of continuedmovement thereof. i

7. A switch comprising a fixed guide, a

contact .mounted and movable upon said guide having a lateral arm, a complemental contact in the line of'movement of the first named contact toward. and away from which the latter is movable, .mans permitting movement of said complemental contact with the other contact in case the said contacts should fuse together, and a short circuit contact arranged at the opposite side. of said 9; Inaswitch of'the character described,

ahollow-screw, a contact supported uponone end of said screw and having a shank entering the bore of the same, said contact being free, except forlthe after mentioned wire,

tomove away from the screw, and a wire connected at one end to said shank and at the other end-to said screw at a distance from its connectionwith the shank, being formed in part as a spring yieldingly retaining said shank in the screw.

10. A device according to claim 9 distinguished by the fact that said wire passes longitudinally through the bore of the screw and is formed as a helix through part of its length, its opposite ends being connected as described to the contact and the screw respectively.

i ll. A temperature governed electric switch comprising .two complemental contacts, having substantially coextensive, parallel con-- "tacting faces of substantial area, one of said contacts being normally stationary. but adjustable, and the other being movable away from and toward the first "contact, holding to permit such adjustment and movement, respectively, and also being arranged to com- 'pel the adjusting movement of the .one

means for the-respective contacts constructed and the-movement of separation and ap proac'li of the other to take place in the same path with preservation atall'times of the parallel relation'of said faces, whereby separation and closing together of the contact faces occur equally at all points in any adjustment, a Bourdon tube so.mounted that its free end is constrained to move in directions approximating those of said path, and

means by which said tube end in the course of its movement in one direction, and at a point determined bythe adjustment of the contacts, removes the movable contact from.

the normally'stationary contact. I

12. A temperature-controlled electric switch adapted to control an electrical heating circuit comprising the combination of a curved elastic member fixed at one end and free at the other end tomove responsively to the effects of temperature changes, a case enclosing said member, a holder mounted in said case, a relatively movable switcn contact held by said holder within the case, means on the holder constructed and arranged to limit the movement of said contact .to a path approximating in directionto the path in which the free end of the elastic member moves, an arm-projecting from said contact transversely to saidv paths, a pin in connec tion with theifree endof said member underlying said arm in position; to engage and move 'the same, and thecontact with it,',wh'en the elastic member is moved in one direction, and a normally stationary complemental contact mounted with provision for adjustpath with the relatively ment in the same movable contact.

adapted to control an electrical heating circuit comprising a Bourdon spring tube, a

case in which said spring tube is contained and in which it is fixed at one end with pro- "vision for admission of fluid to said fixed end, a holder located in said case substantially within the continuation of. the curve 13. Av pressure-operated electric switch,

of the spring tube, a movable switch contact held by said holder, the latter having means for compelling the movement of said contact to take place in a fixed path which extends in generally the same directions in which the free end of the Bourdon tube moves, and the contact having an end contacting face of substantial area transverse to said path, a normally stationary contact mounted with provision for adjustment along the said path and having an end contacting; face within the case complemental in area, contour, and position to the end face of the movable contact, and projections connected to the movable contact and to the Bourdon tube respectively, each crossing the path in which the other moves whereby the tube in the course of its pressure-induced movement in one direction is enabled to displace said movable contact.

14. A temperature-governed electric switch adapted to control an electrical heating circuit, comprising complemental contacts having parallel meeting faces of substantial area, a holderhaving a cylindrical guide portion perpendicular to said faces in'which one of said contacts is fitted to slide endwise, a holder in which the othercontact is mounted with rotatable screw threaded engagement on an axis substantially coinciding with the axis of said guide portion, a temperature-controlled element adapted to be distorted in consequence of temperature changes, and an operatingmeans connected with said element and movable therewith in generally the same directions as the contacts, arranged to displace the first contact from the other contact at a predetermined point in the movement of said element.

In testimony whereof I have affixed my signature.

ALBERT B. COBB. 

